This invention relates to a wire electrode discharge machining apparatus for simultaneously machining a plurality of workpieces into the same configuration with a single wire electrode.
FIG. 1 is a perspective view of a conventional wire electrode discharge machining apparatus, wherein reference numeral 1 designates a wire electrode feed unit, 2 is a wire electrode fed by the unit 1, 3 is an upper guide for the electrode, 4 and 5 are X and Y axis drive units for moving the guide 3, 6 is a workpiece, 7 is a movable table for the workpiece, 8 and 9 are X and Y axis drive units for moving the table 7, 10 is a lower guide for the electrode which extends vertically through the workpiece, and 11 is a receiving or takeup unit which maintains tension on the wire electrode. A supply voltage is applied between the electrode 2 and the workpiece to cause electric discharge therebetween, to thereby cut or machine the workpiece 6. The drive units 4, 5, 8 and 9 move the electrode 2 and the workpiece relative to each other.
When a plurality of workpieces 6, 6a, 6b are to be cut into the same configuration simultaneously, they may be stacked on the movable table 7 as shown in FIG. 2 and then cut in the same manner as described with reference to FIG. 1.
In another arrangement as shown in FIG. 3, a plurality of workpieces 6, 6a (only two shown for simplicity) are mounted on a movable table 7, and feed units 1 and 1a, wire electrodes 2 and 2a, upper guides 3 and 3a, lower guides 10 and 10a and takeup units 11 and 11a equal to the number of workpieces are provided to form a plurality of machining apparatuses with a common movable table. Such apparatuses are operated in the same manner in a real time mode, to thus cut the workpieces simultaneously.
The FIG. 2 method of stacking the workpieces is disadvantageous in that when the workpieces have irregular or bump surfaces gaps are formed between them, as a result of which they are not sufficiently electrically connected to one another and metal powder to be discarded falls into the gaps, thus causing secondary electric discharge. Owing to such secondary discharge the wire may be cut or bent, which results in machining inaccuracies and non-uniformity. Further, when box-shaped workpieces are stacked they are initially clamped together on four sides as shown in FIGS. 4(a) and 4(b). As the machining progresses, however, the number of sides still clamped decreases, as a result of which the workpieces are gradually bent or tilted.
The FIG. 3 method involving a plurality of discharge machining apparatuses is also disadvantageous owing to the intricate construction and high manufacturing cost, and their operations are also difficult to accurately control.